package network2;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;

public class UdpEchoServer {
    private DatagramSocket socket = null;
    public UdpEchoServer(int port) throws SocketException {
        this.socket = new DatagramSocket(port);
    }
    public void start() throws IOException {
        System.out.println("服务器启动成功！");
        while(true){
//            1.读取请求并解析
            DatagramPacket requestPacket = new DatagramPacket(new byte[4096],4096);
            socket.receive(requestPacket);
//            将二进制数据转化为String类型
            String request = new String(requestPacket.getData(),0,requestPacket.getLength());
//            2.根据请求计算响应
            String response = this.process(request);
//            3.把响应写回客户端
            DatagramPacket responsePacket = new DatagramPacket(response.getBytes(),0,response.getBytes().length,
                    requestPacket.getSocketAddress());
            socket.send(responsePacket);

            System.out.printf("[%s:%s] req=%s,resp=%s\n",requestPacket.getAddress(),requestPacket.getPort(),request,response);
        }
    }

    public String process(String request){
        return request;
    }

    public static void main(String[] args) throws IOException {
        UdpEchoServer server = new UdpEchoServer(9999);
        server.start();
    }

}
